High resolution image analyzer with image dissector tube



Oct. 25, 1966 P. c. GOLDMARK HIGH RESOLUTION IMAGE ANALYZER WITH IMAGE DISSECTOR TUBE 7 Original Filed Aug. 31, 1961 INVEN TOR. PETER C. GOLDMARK United States Patent M 3,281,603 HIGH RESOLUTION IMAGE ANALYZER WITH IMAGE DISSECTOR TUBE Peter C. Goldmark, Stamford, Conn., assignor to Columbia Broadcasting System, Inc., New York, N.Y., a corporation of New York Continuation of application Ser. No. 135,377, Aug. 31,

1961. This application Feb. 23, 1965, Ser. No. 440,341 7 Claims. (Cl. 250-219) This is a continuation of application Serial No. 135,- 377, filed August 31, 1961, now abandoned, for High Resolution Image Analyzer.

This invention relates to image analyzing systems for converting an optical image into electrical signals and, more particularly, to a new and improved image analyzer wherein the output signal is characterized by exceptionally high resolution and tonal quality. I

The nonstorage feature of television camera tubes such as the image dissector tube, for example, makes such tubes particularly desirable for use in high resolution image analyzing systems. However, previous attempts to use such tubes for this purpose have not been satisfactory for the reason that the high intensity of illumination of the photosensitive element required for high resolution results in excessive ion bombardment which tends to damage the element and so shorten the life of the tube that its use is not feasible.

Accordingly, it is an object of the present invention to provide a new and improved image analyzing system which avoids the above-mentioned disadvantages of the prior art.

Another object of the invention is to provide an image analyzing system of the above character which is capable of extremely high resolution, of the order of five to ten thousand information elements per line.

A further object of the invention is to provide an image analyzing system which utilizes a form of image dissector tube in such fashion that its effective life is greatly extended.

These and other objects of the invention are attained by providing high intensity illumination of an image hearing medium, optically transferring a selected narrow line portion of the image to the photosensitive surface of an analyzer tube to produce a corresponding narrow line image, and sweeping the resulting electron beam image past a narrow electron collecting slit in a direction substantially perpendicular to the extent of the slit. The image bearing medium, which may be transparent film or opaque paper, is preferably illuminated along a restricted elongated area including the portion of the image to be transferred to the analyzer tube, and the medium is moved in a direction perpendicular to the image line.

In one embodiment of the invention, the illuminated image line is transferred to the photosensitive surface of the analyzer tube by a conventional lens while, in another embodiment, the image transfer is accomplished by a fiber optics device which is interposed directly between the image bearing medium and the analyzer tube. Moreover, a suitable mask may be incorporated in the analyzer tube, the effective photosensitive portion of the latter being confined to a line corresponding to the projected line of the image, thereby eliminating the need for a mask in the optical system.

Further objects and advantages of the invention will be apparent from a reading of the following description, in conjunction with the accompanying drawings, in which:

FIG. 1 is a perspective schematic view illustrating one form of image analyzing system according to the invention;

FIG. 2 is a perspective schematic view showing an Patented Get. 25, 1966 alternative form of illuminating arrangement for the analyzing system;

FIG. 3 is a fragmentary vertical sectional view, greatly magnified, illustrating a modified arrangement for transferring the illuminated imageto the photosensitive surface of the analyzer tube; and

FIG. 4 is a schematic view showing an analyzer for ing to the invention.

In the representative embodiment of the invention shown in FIG. 1, a high intensity ribbon filament lamp 10 backed by a reflect-or 11, is combined with a conventional condensing lens arrangement 12 to project a substantially horizontal line of intense illumination on a longitudinally moving strip of film 13 which bears images to be converted into electrical signals. Immediately adjacent to the film 13 a mask 14 is formed with a narrow, horizontal slit 15 extending the full width of the picture area on the'film so as to define the illuminated film image portion which is to be analyzed at any instant. The slit 15 should be sufficiently narrow to provide the desired resolution in the vertical direction and in a typical case it may be approximately one-half mil wide.' The lamp 10 may be, for example, a watt lamp with a filament about one-half inch long which produces an intensity of illumination at the slit 15 of approximately 5,000 to 10,000 foot candles.

A suitable lens 16 forms a line image 17 of the illuminated film portion on a photocathode 18 formed on the face of an image analyzer tube 19 which is generally of the image dissector type and, with a one-to-one imaging arrangement, the width of the line 17 will be the same as that of the slit 15 i.e., one-half mil. If the lens 16 is arranged to enlarge the image on the photosensitive surface appreciably with respect to the area of the slit 15, because of the high intensity of illumination, the width of the slit 15 may be made even smaller than one-half mil so as to produce a line image 17 which is about onehalf mil Wide. On the other hand, if the lens 16 reduces the image on the photosensitive surface, the slit 15 may be made correspondingly wider so as to produce a line image 17 which is about one-half mil wide.

As in conventional image dissector tubes, the electron image produced by the horizontal line image 17 moves inwardly into the tube and is swept back and forth horizontally by the usual focus and deflection coil system 20, but in the present invention, the electron image is not swept vertically as in conventional image dissector tubes. Moreover, the tube 19 of the present invention utilizes a narrow slit 21 disposed inwardly from the photocathode. The slit 15 should be sufficiently narrow to provide the desired degree of resolution in the horizontal direction and in a typical case it may be about one-half mil wide. This slit is oriented so that it extends perpendicularly to the direction of motion of the electron beam image in the plane of the slit. Consequently, as the electron image of the line is swept past the narrow aperture 21 in sequence, the film image is scanned line by line. Those electrons passing through the aperture 17 at any instant are multiplied by the usual electron multiplier or dynode structure 22, to produce amplified output signals representing line by line the image formation recorded on the film 13.

By reason of the extremely high intensity of illumination of the line image 17 on the photocathode surface 18 necessary for high resolution and the relatively small area of illumination, the current intensity in the electron beam within the tube 19 is several times greater than is normally obtained with image dissector type image analyzer tubes, thereby more than compensating for the images recorded on an opaque medium arranged accordrelatively low sensitivity of this type of tube.

tions in the line image.

At the same time, the effective electron collecting aperture area (one half mil line width by one-half mil slit width) is only about one-hundredth the area of the collecting aperture in conventional image dissector tubes so that a correspondingly greater image resolution is obtained.

More over, even though the current density in the electron beam flowing from the photocathode is much higher than normal, the total current drawn therefrom is the photocathode is illuminated. Consequently, the difiiculties resulting from a large total current drawn from the photosensitive surface encountered in previous attempts to obtain higher resolution in tubes of this type by increasing the illumination are effectively overcome by restricting the illumination to a very narrow line.

In the event that the portion. of the photocathode on which the line is imaged becomes fatigued by continued use, the image can be shifted slightly in the vertical direction on the photocathode so that a new portion of the photosensitive surface is used. Inasmuch as the slit 21 is relatively long, e.g., one-half inch or more, a large number of such vertical shifts of the image line 17 may be made to renew the photosensitive surface portion used without interfering with the operation of the system.

Another advantage of the narrow slit collector arrangement of the present invention which extends perpendicular to the direction of beam motion is that it completely eliminates the effect of any slight variations in the verticalposition of the line image as the electron beam is swept perpendicularly across the slit. Normally, with an aperture of limited extent, such variations can result in failure of part of the line image to be scanned so that part of the picture represented by the output signal may be lost. I

In operation, the film 13 of FIG. 1 is moved in the direction of the arrow past the slit 15 at a rate determined in accordance with the horizontal sweep rate of the tube 19 so that the desired vertical spacing between successive line images of the film record to be reproduced is obtained. It will be apparent from the foregoing that the line images can be as close as one-half mil apart without duplicating any portion of one line in a succeeding line, thereby contributing to extremely high resolution in the vertical direction. If the film image was recorded by a line scan device, the rate of film motion is selected to place each line of the film image at the slit 15 at the time the line image is swept by the tube 19.

The high intensity line image 17 formed on the photocathode 18 causes a corresponding electron beam image to be emitted inwardly within the tube 19 and this beam image is maintained in focus and swept perpendicularly past the slit 21 by the deflection and focusing coil 20 in the usual manner. During this process, the instantaneous electron current passing through the slit 21 is multiplied by the dynode arrangement 22, to provide an amplified output signal representing the intensity varia- If the length of the line image 17 on the photocathode surface is at least two and onehalf inches, it is apparent that a horizontal resolution of more than five thousand elements per line is obtainable with the system of the present invention, assuming unit magnification of the electron image.

A different optical system for providing a horizontal line of intense illumination of the film is illustrated in FIG. 2, wherein the film 13 and the mask 14 with its slit 15 are arranged in the same manner as in FIG. 1. In this case, a point source of light 26 which may be a conventional 100 watt projection lamp may be used rather than the extended source of FIG. 1 and this lamp is positioned between a spherical reflector 27 and a'condensing lens 28 in the usual illuminating system arrangement. In addition, however, two cylindrical condensing lenses 29 and 30 are interposed between the lens 28 and the film 13 so that the light from the source is distributed in a narrow horizontal line of intense illumination on the film. The remainder of this analyzer system and its operation are the same as described above with respect to FIG. 1.

In the greatly magnified sectional view of FIG. 3, an alternative arrangement for transferring the image from the film 13 to the photosensitive surface of an analyzer tube, which may be identical to the analyzer tube 19, is shown. This arrangement, which may be used with either of the illuminating systems described above, comprises a horizontal strip of fiber optics material 31 incorporated into the front plate 32 of the image analyzer tube so as to extend from the photosensitive layer 18 to the outside of the tube. Also, a horizontal slit defining mask may be incorporated in the tube. Thus, a mask 33 containing a narrow horizontal slit 34 may be formed on the inside face of the front plate 12, with a photosensitive layer 18 over it, or at least over the portion containing the slit 34. With this optical transfer system, the film 13 is located immediately adjacent to the outside portion of the strip 31 and driven vertically in the same manner as in FIG. 1.

Within the strip 31 there are a large number of conventional optical fiber elements which are capable of transmitting light from one end to the other without any appreciable lateral scattering. These elements are disposed in closely spaced parallel relation within the strip and extend perpendicularly to the film and to the photosensitive layer 18 within the tube. Preferably, the fiber elements, which are made of glass, are coated with a transparent substance having a low index of refraction to reduce lateral scattering and, in order to obtain the desired high resolution, there must be several fiber elements provided for each information element to be transferred. Thus, with a picture element size of one-half mil by onehalf mil, optical fibers less than one-fifth mil in diameter may be used so that there are at least nine fibers for each element.

In operation, the film 13 in this embodiment of the invention is illuminated with a horizontal line of light in the same manner. as in the previously described embodiments. Each fiber element in the strip 31 transmits light to the photosensitive layer in proportion to the transmission of the corresponding area of the film so that the photosensitive material in the layer 18 is activated to form an electron beam image representing the recorded film information. This image restricted to a narrow line by the slit 34 is analyzed by the tube in the same way as described above with respect to FIG. 1. The part of the face of the analyzer tube that is shielded by the mask 33 is of course unresponsive to the transferred optical image. That is, it does not emit electrons.

Because of the high level of illumination provided in the analyzer system of the present invention, and the high resolution obtainable, it is possible to analyze by reflection techniques information recorded on an opaque medium and FIG. 4 illustrates a form of the invention arranged for this purpose. In this embodiment a sheet of paper or the like having information recorded on one surface 35 is driven between two rolls 36 and 37 along a back-up plate 38 and is illuminated through a mask 39 having a onehalf mil wide horizontal slit 40. A high intensity illuminating system 41, such as the one described above with respect to FIG. 2, may be used to provide an elongated area of illumination at the horizontal slit 40 and an imaging lens 42 focuses the illuminated image on the photosensitive surface of an analyzer tube 4-3 which may be identical to the tube 19 of FIG. 1.

Preferably, in order to avoid the effect of specular reflections, the surface 35 is illuminated at an angle of about 45 degrees and the analyzer tube views the surface perpendicularly, the paper being driven continuously from one roll 36 to the other roll 37. In addition to or in place of the mask 39, a mask 44 having a one-half mil wide horizontal slit may be mounted on the face of the analyzer tube to block out any extraneous illumination.

It will be readily apparent from the foregoing that the present invention provides an image analyzing system which is inherently capable of substantially higher resolution than has been heretofore possible, while at the same time minimizing deterioration of the photosensitive surface of the image analyzer device and greatly extending its useful life.

Although the invention has been described herein with reference to specific embodiments, many modifications and variations therein will readily occur to those skilled in the art. For example, it will be apparent that increased electrical signal amplitudes can be obtained with a slightly greater width for the slit and aperture 21, such as one mil, while still providing improved resolution as compared with conventional analyzer devices. Accordingly, all such variations and modifications are included within the intended scope of the invention as defined by the following claims.

I claim:

1. A system for analyzing intelligence recorded on a transparent record strip in the form of pictorial information consisting of tone density variations and for translating the tone density variations into corresponding electrical video signals representing a high definition image of the pictorial information, comprising: drive means for moving the transparent record strip in the direction of its extent; illuminating means positioned to illuminate an area of the strip at a high intensity level; analyzer tube means including a photosensitive element having a narrow line portion exposed to receive light from the illuminated area; optical transfer means disposed between the illuminated area of the record strip and the analyzer tube means for transferring a high intensity image of the illuminated area to the photosensitive element; masking means adjacent the photosensitive element having an elongate slit extending substantially perpendicularly to the direction of motion of the record strip for restricting the transferred image to a thin line image line and for limiting the excitation of the photosensitive element to a predetermined number of image resolving elements per image line to produce a corresponding thin line electron beam image in the analyzer tube means; aperture means within the analyzer tube means spaced from the photosensitive element and intercepting the electron beam image forming a narrow aperture extending substantially perpendicularly to the direction of extent of the electron beam image in the plane of the aperture, and deflector means for sweeping the electron beam image across the aperture in a direction substantially perpendicular to the direction of extent of the aperture.

2. A system according to claim 1 wherein the optical transfer means comprises a fiber optics device disposed between the record strip and the photosensitive element of the analyzer tube means having optical fibers extending perpendicularly to the photosensitive element and to the record strip and effective to admit to the elongated slit of the masking means a continuous narrow band of light from the illuminated area.

3. A system according to claim 1 wherein the illuminating means comprises a lamp having an elongated filament and condensing lens means projecting a band of uniform intensity light from the filament on the elongated area of the record strip.

4. A system as set forth in claim 3, further comprising reflector means disposed behind the lamp relative to the record strip for intensifying the narrow band of light provided by the lamp to the record strip.

5. A system according to claim 1 wherein the illuminating means comprises a lamp having a ribbon filament of restricted extent in all directions parallel to the extent of the record strip and cylindrical condensing lens means projecting a band of uniform intensity light from the filament on the elongated area of the record strip.

6. A system in accordance with claim 1 wherein the width of the thin image line is about one-half mil in the direction of motion of the record strip, and the narrow aperture has a width of about one-half mil in a direction perpendicular to the direction of motion of the record strip.

7. A system as set forth in claim 1, in which the dimension of the photosensitive element in a direction perpendicular to the direction of elongation of the masking means slit is substantially less than the dimension of the face of the analyzer tube means in that same direction.

References Cited by the Examiner UNITED STATES PATENTS 1,765,029 6/1930 Murray 2502l9 2,432,123 12/1947 Potter 2502l9 2,798,966 7/1957 Summerhayes 2502l9 2,923,781 2/1960 Gordon.

2,967,664 1/1961 Ress 250227 X 3,076,957 2/1963 Hankes et a1 2502l9 X 3,099,750 7/1963 Swarthout et a1. 2502l9 X 3,104,148 9/1963 Archibald et a1. 2502l9 X 3,105,152 9/1963 Nash 250-219 RALPH G. NILSON, Primary Examiner.

I. D. WALL, Assistant Examiner. 

1. A SYSTEM FOR ANALYZING INTELLIGENCE RECORDED ON A TRANSPARENT RECORD STRIP IN THE FORM OF PICTORIAL INFORMATION CONSISTING OF TONE DENSITY VARIATIONS AND FOR TRANSLATING THE TONE DENSITY VARIATIONS INTO CORRESPONDING ELECTRICAL VIDEO SIGNALS REPRESENTING A HIGH DEFINITION IMAGE OF THE PICTORIAL FORMATION, COMPRISING: DRIVE MEANS FOR MOVING THE TRANSPARENT RECORD STRIP IN THE DIRECTION OF ITS EXTEND; ILLUMINATING MEANS POSITIONED TO ILLUMINATE AN AREA OF THE STRIP AT A HIGH INTENSITY LEVEL; ANALYZER TUBE MEANS INCLUDING A PHOTOSENSITIVE ELEMENT HAVING A NARROW LINE PORTION EXPOSED TO RECEIVE LIGHT FROM THE ILLUMINATED AREA; OPTICAL TRANSFER MEANS DISPOSED BETWEEN THE ILLUMINATED AREA OF THE RECORD STRIP AND THE ANALYZER TUBE MEANS FOR TRANSFERRING A HIGH INTENSITY IMAGE OF THE ILLUMINATED AREA TO THE PHOTOSENSITIVE ELEMENT; MASKING MEANS ADJACENT THE PHOTOSENSTIVE ELEMENT HAVING AN ELONGATE SLIT EXTENDING SUBSTANTIALLY PERPENDICULARLY TO THE DIRECTION OF MOTION OF THE RECORD STRIP FOR RESTRICTING THE TRANSFERRED IMAGE OF A THIN LINE IMAGE LINE AND FOR LIMITING THE EXCITATION OF THE PHOTOSENSITIVE ELEMENT TO A PREDETERMINED NUMBER OF IMAGE RESOLVING ELEMENTS PER IMAGE LINE TO PRODUCE A CORRESPONDING THIN LINE ELECTRON BEAM IMAGE IN THE ANALYZER TUBE MEANS; APERTURE MEANS WITHIN THE ANALYZER TUBE MEANS SPACED FROM THE PHOTOSENSITIVE ELEMENT AND INTERCEPTING THE ELECTRON BEAM IMAGE FORMING A NARROW APERTURE EXTENDING SUBSTANTIALLY PERPENDICULARLY TO THE DIRECTION OF EXTENT OF THE ELECTRON BEAM IMAGE IN THE PLANE OF THE APERTURE, AND DEFLECTOR MEANS FOR SWEEPING THE ELECTRON BEAM IMAGE ACROSS THE APERTURE IN A DIRECTION SUBSTANTIALLY PERPENDICULAR TO THE DIRECTION OF EXTENT OF THE APERTURE. 